If you have the setting for interrupted cutting (for doing things like expanded metal) on your Hypertherem then you can go over slots and it should keep the arc going. It's on a settings selector knob on the front of the machine (at least it is on my PM85).

I cut over existing cuts all the time and this is how I do it.
-In sheetcam highlight the operation you want to do this with.
-go to Mode, edit action points. Move to the location on the drawing you want to go over an existing line. Boxes will appear that require information. This is what I use:
Length - 1inch Feedrate - 100% Start Code - Code C2 DTHC on End Code - Code C1 DTHC off.

You will also need to put a check in the "Disable Hold" so when the arc signal is lost the torch does not just stop.

FazQuaz wrote:I cut over existing cuts all the time and this is how I do it.
-In sheetcam highlight the operation you want to do this with.
-go to Mode, edit action points. Move to the location on the drawing you want to go over an existing line. Boxes will appear that require information. This is what I use:
Length - 1inch Feedrate - 100% Start Code - Code C2 DTHC on End Code - Code C1 DTHC off.

You will also need to put a check in the "Disable Hold" so when the arc signal is lost the torch does not just stop.

I'll be danged. This is good to know! I'll have to give this a shot! I didn't know I could choose -specific- points on the toolpath for actions.

I forgot to mention, that I break up the drawing into lines that are vertical and horizontal and put them on different layers. I cut the vertical lines first (on its own layer) and then cut the horizontal. The horizontal cut (or layer) will be cutting over the vertical layer and will require the instructions I mentioned above. I hope this makes sense!